Black-hearted galaxy
Marcus Chown suggests explanations for the observation of only bright, young stars at the Milky Way’s heart (18 September, p 30), but neglects to address the fact that conditions at the centre of the galaxy may just favour the formation of massive stars.
Alternatively, the massive stars and black hole at the centre of the galaxy may throw smaller stars out of the galaxy’s heart, because lighter stars would be subject to gravitational slingshot effects much more than more massive ones. If this happened early on in their formation, it would skew the ratio of stars that were left behind.
In essence, as gas moved towards the galaxy’s centre to fuel star formation, some would fall into the central massive black hole, generating pulses of radiation and winds that would quickly clear the gas away. Any lower-mass objects might also be ejected in violent gravitational interactions with the central black hole and the massive stars. After a while the star formation would stop, leaving only what you see: outward-moving lower-mass stars.
If this process happened often enough you could get shells of stars of different ages inside the centre of the bulge, which could be detected in surveys. Each shell would represent a pulse of star formation followed by ejection from the nucleus of the galaxy.
Probably atheism
I have a problem with David Eagleman’s “possibilianism”, the idea that we do not have enough information to rule out either religion or atheism, so should actively pursue all the possibilities (25 September, p 34).
The distinction is between the possible and the probable. Much as I would love to entertain the possibility of Terry Pratchett’s Discworld being carried through space on the back of a giant turtle, this is probably not the case. Thus perhaps “probabilianism” would be a more apt concept.
When it comes to the justifications and so-called research underpinning many religions, we have to ask ourselves how valid it is, who carried it out and why did they come to their conclusion. A more cynical person than me might think the ingestion of certain interesting plant substances could have been involved. Not to mention the attraction of three square meals a day on the part of the early practitioners, and a reprieve from hard manual labour in exchange for some heavy chanting.
Basically, the conflict between theists and atheists is pointless since they are not speaking the same language. Probably.
From Liam Appelbe
In his article, Eagleman demonstrates a common misunderstanding of the term “atheism”. Atheism is simply the lack of belief in a god; it is not the belief that no god exists. None of Eagleman’s “new atheists” claims to know with certainty that a god doesn’t exist. Indeed, Richard Dawkins made this quite explicit, writing a chapter in The God Delusion specifically named “Why there almost certainly is no God”.
Eagleman asserts that “when there is a lack of meaningful data to weigh in on a problem, good scientists are comfortable holding many possibilities at once, rather than committing to a particular story over others”. Not so: scientists should certainly reserve judgement on hypotheses that lack data either way, but the default position is not to hold all the possibilities at once, but rather to not hold any of them. The scientific approach is to reject the claim that God exists until the burden of proof is met.
The possible world views that Eagleman believes are excluded from the God debate are all atheistic world views 鈥� they don’t posit a God. “Possibilianism” is consistent with atheism, but if Eagleman is really that uncomfortable with the atheist label, why doesn’t he just call himself an agnostic?
Carlton, Victoria, Australia
Brain training
Although brain training games may not work (2 October, p 28), some types of structured cognitive training, usually but not exclusively computer-delivered, can improve working memory by increasing dopamine receptor density in the prefrontal cortex ().
Indeed, specific cognitive training is the only known treatment for the cognitive deficits associated with schizophrenia, and there are comparable effects for several developmental and age-related disorders.
One must not get carried away by the negative results in a single well-publicised paper such as the one by Adrian Owen and his colleagues (), which found that an average of 10 minutes per day, three to four days per week of non-specific brain training, delivered as part of a UK television experiment, did not generalise to other cognitive tests. It is perhaps misleading to write that “no large, published trial has yet shown concrete evidence that brain training has an effect on real world activity”. There are no large-scale trials of thousands, because only a television-sponsored trial could fund this. But there are a large number of small, very well-controlled trials published in highly reputable journals showing consistent effects of particular types of cognitive training given at adequate dosages.
From Roger Malton
Your article outlines the way in which practical music-making helps to develop the brain. Has similar research been done into the positive effects of dance?
Some forms of dance such as ballet, Scottish step and highland dancing require not only accurate timing in response to music, but also an ability to maintain accurate physical positions. In many forms of social dance there also has to be a simultaneous response to a dance partner or other members of a group or team, not to mention some degree of physical exertion.
Newcastle upon Tyne, UK
No universal paradox
Rachel Courtland reports that a paradox exists in the theory of eternal inflation, which gives rise to the multiverse, because of a mathematical model in which it is only possible to calculate the probabilities by enforcing artificial boundaries (2 October, p 6). Alan Guth of MIT asserts that the supposed paradox is merely an artefact of the mathematical treatment of the problem. I agree: if the application of the technique leads to a paradox, this should be grounds for dismissing it.
Regarding the thought experiment described in the article, where someone flips a coin to determine whether they should be woken after a short or long sleep, we do not need to postulate an infinite number of universes coming into existence to see that the probability of heads or tails is not the same as the probability of finding someone awake at any given time.
Furthermore, the argument conflates the idea of “infinite” with that of “all encompassing”. Just because there might be an infinite number of universes springing up over an infinite amount of time, there is no guarantee that any event we can imagine is possible in all of these universes. There could very well be constraints on these universes which could cause the coin toss in the alarm clock thought experiment to come up “heads” much more frequently than “tails” in all of these universes.
The key here is specifying what “can” happen in these infinitely emerging universes, and I do not think that the people who are considering the theory of eternal inflation have any idea what that might be.
If the theoretical application of what they specify can happen leads to impossible or highly unlikely conclusions, then this says a lot more about the validity of their assumptions and theory than about the real universe that we live in.
Happiness is鈥�
Dan Jones’s article on happiness (25 September, p 44), provided an intriguing conjugation with research (4 October 2003, p 44) showing that those who have religious beliefs are happier and more satisfied with life.
The five methods to boost positive emotions that were outlined in Jones’s article are congruous with the most important tenets taught in Christianity and other religions: avoid consumerism, nurture and build relationships (easy when churches are ready-made families), practise meditation (prayer), reject bad thoughts, and keep a prayer diary, which will quickly fill up with written examples of positive experiences.
Of course, there is a lot more to being happy and devout than just five things, but these are a good start. It is interesting to note how little human needs have changed during the past 2000 years. We still need to be happy, and the route to happiness has not changed.
From Roger Taylor
Your editorial mentions that surveys of life satisfaction indicate that our optimum level is around 7 or 8 out of 10 (25 September, p 5). I would suggest that the explanation lies in our ability to feel empathy.
We have evolved with survival instincts that make us put ourselves first. Empathy is part of this: we ensure our own well-being in our society by looking after each other. Such selfless behaviour is ignored at our emotional peril.
We each deal as best we can with matters necessary to achieve happiness: the balance of our needs and wants, valuing what is good in our lives, the recognition of what we can change and what we cannot. But given that so many others in this world are both beyond our immediate individual help yet suffering greatly, our hard-wired empathy will not allow complete happiness. Instead, it keeps us restless and searching, which is no bad thing, both individually and socially.
Meols, Merseyside, UK
Shady mutants
The most interesting news in your article on improving photosynthesis seemed to be tucked away in a small paragraph about soybeans: a mutant variety of soybean with half the usual amount of chlorophyll actually yields 30 per cent more biomass (11 September, p 40). The explanation is that plants evolved to produce excess chlorophyll to allow them to compete in shady environments. This can prove costly to the plant, as excess light energy must be mopped up by a “quenching system” before it damages the leaves.
While this may be considered a small improvement in a single crop, it is big news when considering multi-crop systems where productive species are “stacked” on top of one another as in a real ecosystem. If all the plants in such a system were using just the sunlight they needed rather than competing for maximum sun, the improvements would be multiplied.